Rapid blood loss is particularly difficult to control. Attempts have been made to develop a haemostatic sponge which provides a fast and effective composition for inducing rapid blood coagulation and hemostasis at a wound or bleeding site. One such haemostatic sponge composition is an absorbable gelatin sponge. The spongy physical properties of the gelatin sponge hasten clot formation and provide structural support for the forming clot.
Gelatin sponges are made by foaming a solution of gelatin and drying the foam, usually by lyophilization. Unlike collagen which is naturally insoluble in aqueous solutions, gelatin is soluble at temperatures above 30° C., especially at 37° C.—the body temperature. This characteristic renders the sponge unsuitable for in vivo use as the sponge would dissolve quickly and lose its structural integrity and porous structure. The gelatin must therefore be cross-linked in order to prevent its dissolution in the blood. Methods of cross linking include treatment of the sponge with a chemical cross-linking agent such as formaldehyde, glutaraldehyde, and carbadiimides (e.g. EDC) or treatment of the dry sponge with dry heat (100-160° C. for several hours).
While its mode of action is not fully understood, it is currently believed that its effect appears to be linked to the ability of the gelatin sponge to absorb and hold within its interstices, many times its weight of blood and other fluids. Caught blood platelets interact with the sponge and get activated leading to the formation of a haemostatic plaque and cessation of bleeding. This haemostatic plaque resembles the natural plaque that usually forms after injury. The activated platelets also initiate the coagulation cascade that ends with conversion of soluble fibrinogen into a net of insoluble fibrin by the action of thrombin. Factor XIII which is activated by thrombin in the presence of Ca2+ cross-links and stabilizes the clot's fibrin monomers.
GELFOAM and SURGIFOAM Powder are an example of haemostatic devices which can be applied directly to the wounded site with or without thrombin to obtain cession of bleeding. In order to enhance the natural haemostatic property of gelatin, products or kits that combine the haemostatic features of gelatin, thrombin and Ca2+ have been developed and manufactured. For example, it is customary that in surgery the gelatin sponge is removed from its package, dipped into diluted thrombin solution and kneaded vigorously until all air is expelled. This step is followed by a second immersion in thrombin solution and application of the wet sponge to the bleeding organ with light pressure. However, the soaking and coating of the sponge requires time-consuming and cumbersome procedures, including freezing, thawing and pre-dilution of the concentrated thrombin solution. Each of the preparation steps introduces potential errors which might compromise the sterile preparation and vary the efficacy of the sponge. Moreover, the complicated procedure requires administration of the sponge by trained emergency personnel. Another major drawback in the pre-wetting technique is that a large volume of liquid is required to fill the sponge voids consequently resulting in low thrombin and Ca2+ concentration at the interface between the sponge and the injured site. As a result, the sponges are ineffective in providing and maintaining haemostasis. To overcome this problem, surgeons often resort to the use of high concentrations of thrombin, which can lead to the development of a thrombogenicity risk.
Another problem with certain commercially available gelatin sponges comprising dry thrombin is their lack of flexibility in the dry state. These haemostatic devices do not conform easily to the shape of the body surface to which it is applied. Therefore, it is desired to obtain such all in one ready to use gelatin sponge comprising dry thrombin which easily conforms to the contours of a biological surface, making the manipulation of applying the sponge quicker to perform. Accordingly, blood loss is minimized and valuable surgical time is saved.
U.S. Pat. No. 5,643,596 and WO9512371 disclose an effective haemostatic patch comprising a matrix and at least one haemostatic agent, epsilon aminocaproic acid (EACA) on a single side of a flat patch, namely, the wound-contacting surface. The patch does not contain fibrinogen. According to the description EACA is an important feature, because, surprisingly, it has been discovered that EACA functions as a hemostatic agent in the patch in a manner that approximates the effectiveness of fibrinogen, a coagulation factor. The applicant indicates that surprisingly EACA in the matrix of a patch provides an alkaline environment that accelerates activation of thrombin in comparison with thrombin activation in the absence of EACA. The thrombin can be present in the blood and optionally thrombin provided as an exogenous ingredient of the patch mixed with the alkaline solution in the local environment of the patch. The applicants indicate also that EACA possesses antibacterial properties. A biodegradable matrix, such as absorbable gelatin sponge or calcium alginate, collagen, and oxidized cellulose comprising the EACA on the wound-contacting face of the sponge is disclosed. According to the description, the dry matrix can be applied with or without pre-moistening. According to the description the preferably amount of thrombin that can be applied to the wound-contacting surface is 2-10 IU/cm2. The thrombin component facilitates EACA's adherence to the matrix. The patent application is silent on a biodegradable matrix without EACA.
WO9013320 relates to a dry haemostatic sponge comprising a porous structure of biologically absorbable, solid material containing thrombin, and one or more thrombin-stabilizing agent. The patent discloses several materials for the preparation of the haemostatic sponge, such as collagen, gelatin, chitin, cellulose, polyglycolic acid and polylactic acid. The hemostatic biologically absorbable sponge is prepared by injecting an aqueous solution of thrombin at a multiplicity of sites. The sponge is vacuum dried. According to the description, the injection of thrombin or the extrusion under reduced pressure may result in a sponge that is damaged in key functional/structural characteristics.
U.S. Pat. No. 2,558,395 disclose a ready-to-use gelatin sponge containing thrombin. According to the patent, thrombin is added to an aqueous gelatin solution, transformed into foam and dried in a vacuo at low temperature. The gelatin in this patent was not cross-linked at any stage during the preparation. Thus, upon contact with blood, the gelatin component is dissolved, the thrombin is released immediately and causes the transformation of fibrinogen to fibrin and a fibrin film is formed over the wound.
U.S. Pat. No. 4,292,972 relates to a lyophilized foam sponge product which has a hydrocolloid composition. According to the description the solubility and absorbability of the lyophilized foam product can be reduced by cross-linking either before or after the lyophilization procedure. The lyophilized foam product is formed from a mixture of gelatin, pectin and sodium carboxymethylcellulose.
U.S. Pat. No. 4,265,233 disclose a wound healing material to which thrombin and Factor XIII have been fixed by covalent or ionic bonding. According to the description the wound healing material may be synthetic or naturally polymers. The patent discloses several natural occurring proteins, including Cellulose, viscose rayon, cupraammonium rayon, cellulose acetate, carboxymethyl cellulose, methyl cellulose, agarose, dextran, pullulan, pectin, alginic acid, chitin, polysaccharides such as mucopolysaccharides, and proteins such as wool, silk, collagen, gelatin and casein. The patent does not mention a specific composition of the wound healing material. The examples also disclose that the preparation involves dipping the preformed sponge in an aqueous solution of thrombin and Factor XIII and subsequent freeze-drying for 20 hours.
EP0277096 discloses a hemostatic material, such as GELFOAM®, SURGICEL®, and AVICEL®, and collagen which are used in combination with a stabilized thrombin composition. According to the patent the preparation must contain glycols and acetate buffer or phosphate buffer. According to the description the stabilized solution is preferably absorbed onto the hemostatic agent and the pad is freeze-dried and packaged in a sterile manner. In the description it is indicated that Freeze-drying may result in a sponge with low flexibility.
There are also dry fibrin sealant absorbable dressings developed by collaborative efforts between the American Red Cross and the US Army. The dressing consists of two outer layers of human fibrinogen and a middle layer of human calcium chloride and thrombin, freeze-dried onto an absorbable Dexon mesh backing. There are concerns about the durability and friability of the bandage for field use. The dressings are fragile and tend to break apart if not handle carefully. Also, the cost of this dressing is high (Mc Manus and wedmore Business briefing: emergency medicine review 2005).
A dry ready-to-use effective hemostasis dressing for control of hemorrhage, and whose use is easy and does not require any specific training; that is sterile; inexpensive; flexible; and durable is a long felt need. Particularly, there is a need for the development of an “all in one” ready-to-use gelatin sponge that contains highly concentrated and thin layer of an active protein/peptide active compound, such as thrombin, on the sponge surface that adheres to the wound and which maintains the original key structural characteristics such as height, texture and appearance of the gelatin sponge.